• Title/Summary/Keyword: Residual stress

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A Study for Mitigating Residual Stress in CRDM Penetration Nozzle Weld (제어봉구동장치 관통노즐 용접부의 잔류응력 완화를 위한 연구)

  • Lee, Seung-Gun;Kim, Jong-Sung;Jin, Tae-Eun
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.90-95
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    • 2004
  • In this study, we proposed new method to mitigate tensile welding residual stress for preventing PWSCC in CRDM nozzle. Residual stress analysis using finite element method is performed to confirm benefit of the new method. In case of applying existing method, tensile axial residual stress decrease by about 28% and tensile hoop residual stress decrease by about 33%. In case of applying the new method, tensile axial residual stress decrease by about 32% and tensile hoop residual stress decrease by about 43%. Therefore, we conclude the new proposed method is more effective to prevent PWSCC than existing method.

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A Study on Residual Stress Characteristics for Joint of Rock in Ring Shear Tests (링 전단시험기를 이용한 암석절리의 잔류강도 특성에 관한 연구)

  • 권준욱;김선명;윤지선
    • Journal of the Korean Geotechnical Society
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    • v.16 no.6
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    • pp.35-41
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    • 2000
  • Residual stress is defined as a minimum stress with a large displacement of specimens and the residual stress after peak shear stress appears with displacement volume but there is no provision to select the residual stress. In the previous study, residual stress was recorded when the change of shear load is small in the condition of the strain more than 15%. But, in this study, hyperbolic function((No Abstract.see full/text), b=experimental constant) of soil test is adapted to joint of rock and the propriety is investigated. In a landslide and landsliding of artificial slope, wedge failure of tunnel with a large displacement, tests are simulated from peak stress to residual stress for safety analysis. But now. direct shear stress and triaxial compressive tests are usually performed to find out characteristics of shear stress about joint. Although these tests get a small displacement, that data of peak stress and residual stress are used for safety analysis. In this study, we tried to determine failure criteria for joints of rock using ring shear test machine. The residual stress following shear behavior was determined by the result of ring shear test and direct shear test. In conclusion, after comparing the results of the two test, we found that cohesion(c) and internal friction angle(ø) of ring shear test are 30% and 22% respectively of those of the direct shear test.

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Fatigue Life Evaluation Based on Welding Residual Stress Relaxation and Notch Strain Approach for Cruciform Welded Joint (용접잔류응력 이완 및 노치변형률법을 적용한 십자형 필렛용접 이음부의 피로수명 평가)

  • Han, Jeong-Woo;Han, Seung-Ho;Shin, Byung-Chun;Kim, Jae-Hoon
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1103-1108
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    • 2003
  • The fatigue strength of welded joint is influenced by the welding residual stress which is relaxed depending on local stress distributed in vicinity of stress raisers, eg. under cut, overlap and blow hole. To evaluate its fatigue life the geometry of the stress raisers and the welding residual stress should be taken into account. The several methods based on notch strain approach have been proposed in order to consider the two factors above mentioned. These methods, however, have shown considerable differences between analytical and experimental results. It is due to the fact that the amount of the relaxed welding residual stress evaluated by the cyclic stress-strain relationship do not correspond with that occurred in reality. In this paper the residual stress relaxation model based on experimental results was used in order to reduce the discrepancy of the estimated amount of the relaxed welding residual stress. Under an assumption of the superimposition of the relaxed welding residual stress and the local stress, a modified notch strain approach was proposed and verified to the cruciform welded joint.

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A Study on the Development of Stress Optic Law Considering Residual Stress in Photoelastic Experiment(II) -Application of Stress Optic Law Considering of Residual Sterss- (잔류응력을 고려한 광탄성실험의 광응력법칙 개발에 관한 연구 (2) -잔류응력을 고려한 광응력법칙의 응용-)

  • 서재국;황재석;최선호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1810-1821
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    • 1995
  • Photoelastic experiment has been used to analyze stress of structure and stress in the vicinity of crack tip etc.. Model experiment such as photoelastic experiment has been restricted by problem of residual stress in the photoelastic model material. They are generated by molding, cutting and time effects etc.. They produce some errors in the results of photoelastic experiment data. In this paper, stress optic law considering residual stress already developed by authors was applied to the stress concentration problem and fracture mechanics. Although the specimen was bad with residual stress, we could obtain good results by using the stress optic law considering residual stress. It was found that the stress optic law of photoelastic experiment could be applied to the stress analysis of bimaterial.

Sensitivity Analysis of Heat Source Parameter for Predicting Residual Stress Induced by Electron Beam Welding (스테인리스강에 대한 전자빔 용접 잔류응력 예측을 위한 열원 변수 민감도 해석)

  • Shin Je Park;Hune Tae Kim;Yun Jae Kim
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.18 no.2
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    • pp.61-68
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    • 2022
  • Accurate evaluation of residual stress is important for stress corrosion cracking assessment. In this paper, electron beam welding experiment is simulated via finite element analysis and the sensitivity of the parameters related to the combined heat source model is investigated. Predicted residual stresses arecompared with measured residual stresses. It is found that the welding efficiency affects the size of the tensile residual stress area and the magnitude of maximum longitudinal residual stress. It is also found that the parameter related to the ratio of energy distributed to the two-dimensional heat source has little effect on the size of tthe tensile residual stress area, but affects the size of the longitudinal residual stress in the center of the weld.

Stress Analysis of the Micro-structure Considering the Residual Stress (잔류응력을 고려한 미세구조물의 강도해석)

  • 심재준;한근조;안성찬;한동섭
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.820-823
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    • 2002
  • MEMS structures Generally have been fabricated using surface-machining, but the interface failure between silicon substrate and evaporated thin film frequently takes place due to difference of linear coefficient of thermal expansion. Therefore this paper studied the effect of the residual stress caused by variable external loads. This study did not analyzed accurate quantity of the residual stress but trend for the effect of residual stress. Several specimens were fabricated using other material(Al, Au and Cu) and thermal load was applied. The residual stress was measured by nano-indentation using AFM. The results showed the existence of the residual stress due to thermal load. The indentation area of the thermal loaded thin film reduced about 3.5% comparing with the virgin thin film caused by residual stress. The finite element analysis results are similar to indentation test.

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Finite Element Analysis of Effect of Preheating on the Residual Stress in 304 Stainless Steel Weldment (304 스테인레스강 용접부 잔류응력에 미치는 예열 효과의 유한요속 해석)

  • 장경복;김하근;강성수
    • Journal of Welding and Joining
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    • v.16 no.5
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    • pp.67-75
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    • 1998
  • This study aimed at he experimental and finite element analytic investigation of the effect of preheating on he residual stress of weldment. In this study, an autogenous arc welding was used on type 304 stainless steel and MARC as F.E.M. common code was utilized in analysis The analyses include transient and moving heat source and thermal properties as function of temperature. During welding, the thermal cycles of four locations in the weldment were recorded to investigate of the behavior of thermal stress and residual stress. The experimental and analytic results had good coincidence and show that there are two factors influencing the formation of welding residual stress in preheat process. One is the elevation of welding equilibrium temperature and the other is the increase of amount of heat input. The former decrease welding residual stress and the latter increase welding residual stress. Therefore, the cumulative effects result in the welding residual stress not being improved significantly with preheating in 304 stainless steel.

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Evaluation of High Temperature Strength Characteric in Joint Metal (접합재의 고온강도 특성 평가)

  • Huh, Sun-Chul;Park, Young-Chul;Yun, Han-Ki;Park, Won-Jo
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.103-108
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    • 2000
  • Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

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Effect of Residual Stress on Fatigue Characteristics at the Welds of Stainless Steel (스테인리스강 용접부의 잔류응력이 피로특성에 미치는 영향)

  • 권종완;양현태
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.5
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    • pp.110-117
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    • 2001
  • In the weldments, the crack propagation rate is changed due to the residual stress. The crack propagation rate is high in the region with the residual stress. However it shows the same behavior with the base metal in the region that does not include the residual stress. The fatigue crack growth rate for the material with residual stresses can be predicted more precisely by using the effective stress ratio. The difference between experimental results and prediction results seems to be due to the redistribution of the residual stresses and microstructural change.

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Application of Laser Interferometry for Assessment of Surface Residual Stress by Determination of Stress-free State (무잔류 응력상태 결정을 통한 표면 잔류응력장 평가에의 레이저 간섭계 적용)

  • Kim, Dong-Won;Lee, Nak-Kyu;Choi, Tae-Hoon;Na, Kyong-Hoan;Kwon, Dong-Il
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.25-30
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    • 2003
  • The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI). The residual stress fields in case of both single and film/substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 ${\mu}m$ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the x-ray diffractometer (XRD) for the verification of above residual stress results by ESPI.

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